This specific objectives of this subproject are to (1) characterize the extent and nature of chromosomal and genic variability in populations of certain rodent and insectivore species; (2) identify the coccidian parasite faunas of these host species; (3) attempt to correlate speciation of the coccidian genus Eimeria with genetic variation and/or ecological distribution patterns of the host populations; and (4) over the long term, use the karyotypic and electrophoretic data on host populations to investigate the role that various loci may play in susceptibility of these hosts to their specific parasite faunas. Our hypothesis is that host specificity and evolution in the coccidian genes Eimeria are determined by host genetics and distribution patterns. Data from previous studies in squirrels, cricetid rodents, moles, shrew- moles, and bats are beginning to support these ideas and during the next four years we will continue to analyze tissue, chromosome and parasite samples from hosts that were collected from 1981 through 1986 as well as collect more hosts and parasites from around the world. Once all the specific pieces of data have been individually itemized (chromosomes counted and banded; gels run and enzyme variation qualified and quantified; parasites measured, identified and described) we should begin to realize the specific objectives listed above. One interesting development that has occurred recently involves Dr. Yates' new research in the South American country of Bolivia. This project, funded by NSF, is generating large samples of mammals and parasites that will allow independent tests of our ideas from Asian and North American species. It may turn out that one of the most immediate applications of our findings will be in South America where parasite diseases are a major health problem. We are currently establishing convenios with the two major tropical disease centers in Bolivia. If successful, this should provide major positive opportunities for use and our MBRS students.